Injected sealing compound systems have been introduced as an alternative to expensive mechanical seals used with rotating shafts or braided compression packing used with rotating or reciprocating shafts, e.g., in pumps, compressors, or other apparatus. Unlike mechanical seals and braided compression packing, injectable sealing compounds are self-lubricating, eliminate leakage, need no cooling water or flush water, and do not damage shaft sleeves. Injectable sealing compound systems therefore can substantially reduce or eliminate flush water consumption and equipment maintenance, resulting in substantial savings. See, e.g., Glowacki, "Mills Use New Sealing Compound to Minimize Water Consumption," Pulp and Paper, November, 1995, 97-98.
In an injectable sealing compound system, a stuffing box provided with a fluid injection port surrounds a rotating or reciprocating shaft that extends through the stuffing box bore. A sealing means (e.g., braided packing rings, gasket rings, restriction bushing, taper rings) concentrically surround the shaft at opposite ends of the stuffing box bore. The space between the packing seal rings is filled with an injectable sealing compound that is injected under greater than atmospheric pressure into the stuffing box through an injection port. The packing rings or other sealing means depend on the injectable sealing compound to hold them in place.
Leakage of the injectable sealing compound from the stuffing box can cause the packing seal rings or other sealing means to move toward each other. If one of the packing seal rings blocks or moves past the injection port, it is necessary to shut down the machinery and reposition the rings before resealing. If a packing seal ring opens up at its joint, sealing compound can escape from the stuffing box.